JPH01165732A - Production of porous metal casting - Google Patents

Abstract

PURPOSE:To produce a porous metal casting having stable quality and withstanding the external pressure, which is suitable as a implant such as an artificial bone, by forming a porous wax model from a model consisting of solvent-soluble granules and wax, forming a casting mold with the wax model and casting a molten metal by lost wax process. CONSTITUTION:Granules 3 of a solvent-soluble inorg. or org. compd. having about 200-500mum diameter are packed into the cavity 2 in a mold 1 consisting of a cope 1a and a drag 1b and wax 4 is injected into the cavity 2 to form a model. This model is taken out of the mold 1 and the granules 3 are removed by dissolution in the solvent to obtain a porous wax model 6. A slurry 11 of CaO, etc., is filled into the pores in the model 6 to form a shell and an outer frame 12 of sand is formed around the shell. The wax 4 is then melted and removed to form a casting mold (lost wax casting mold) 10. A molten metal is poured into the mold 10 from a sprue 13 and solidified, the frame 12 is removed and sand grains entering the pores 9 in the resulting porous metal casting 8 are removed. The casting 8 which is hardly broken by load such as the external pressure is obtd. at a low cost.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is applicable to porous implant materials made of titanium or titanium alloy, which are mainly used for implantation in the human body, such as orthopedic artificial bones and dental artificial tooth roots. The present invention relates to a method for manufacturing a quality metal casting.

<Prior art and its problems> Porous metal bodies having pores connected to each other on the surface or inside of the metal body are often used for printing bodies, melting cores of kerosene stoves, bearings, filters, soundproofing materials, molds, etc. On the other hand, materials with roughened surfaces using, for example, titanium or titanium alloy as the metal are increasingly being used as implant materials for human body implants.

The method for roughening the surface of this bioimplant material is as follows:
JP-A-62-74004 discloses a method in which a mixed powder of titanium or titanium alloy powder and acid-soluble metal powder is diffusion bonded to the surface of titanium or titanium alloy material, and only the acid-soluble metal powder is dissolved and removed by acid. has been done.

Also, Special Publication No. 62-30253, No. 62-30254
As disclosed in the above publication, a molten metal or alloy is press-fitted into a molded body made of easily water-soluble salt powder or solvent-soluble inorganic compound powder particles, and after it solidifies, the soluble powder particles are melted and removed. There is a method of obtaining a porous metal body.

The former method is basically the same as the usual method of sintering and fixing titanium or titanium alloy powder, and has the drawback that the joint part breaks when a load is applied, and the joint particles are easily removed.

In addition, the latter requires a large press machine and a sturdy casting flask in order to inject molten metal or alloy under high pressure into a porous body connected with easily water-soluble salt-baked road bodies or solvent-soluble inorganic compounds. limited to low melting point metals or alloys.

In particular, in Japanese Patent Publication No. 82-30254, a pressure of 1 to 20 ton/cm" is usually required to obtain a molded product, and the mold cannot be used repeatedly.

Furthermore, both methods are limited to products with simple shapes due to their manufacturing methods, and cannot be applied to products with complex shapes.

<Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and it is possible to use a metal or alloy that has proof strength against the load and has a high melting point, and is easy to manufacture. It is an object of the present invention to provide a method for manufacturing a porous metal body in which the process is simplified, the mold can withstand continuous use, and production costs can be reduced.

More specifically, for example, a manufacturing method that attempts to integrally mold a spongy porous layer that provides excellent bone bonding properties on the surface of an artificial bone made of titanium or titanium alloy by means of casting, using an easy method. is provided.

Among porous metal bodies, porous metal bodies using titanium or titanium alloys have excellent performance as biomaterials, and are suitable for use in orthopedic artificial bones and dental artificial bones. Demand is rapidly increasing as a material for tooth roots.

By the way, the bone tissue of the human body consists of unit tissues of 200 to 300 μm, and when an artificial bone is implanted into the human body, these bone tissues grow to surround the artificial bone, and the bone and the artificial bone are integrated into one. . For this reason, the surface of the artificial bone that connects with the bone has an uneven shape with an interval of about 200 to 300 μm, or even has countless interconnected pores in the lower part of the surface, that is, it is a spongy porous material. It is best that

A variety of studies have been carried out with these objectives in mind, but most of them involve adding irregularities using various methods after processing the material. These methods have complicated processes and low productivity;
Considering the purpose of increasing the integration with bone tissue, a satisfactory effect may not necessarily be obtained.

Therefore, in order to solve the above problems, the present inventors have conducted intensive research and found that when manufacturing a porous metal body, (1) means for integrally manufacturing the material and the porous layer on the surface thereof; Precision casting (lost wax method) is used.

(2) In order to achieve the above object, the surface of the wax agent model is made into a porous layer.

(3) As a means to easily obtain a porous layer on the surface of the wax agent model, prepare soluble inorganic or organic compound particles that are connected to each other and are partially exposed on the surface of the wax agent model, and coat them with an acid or an organic solvent. Melt and remove.

The inventors have discovered that by employing this method, a porous metal body that achieves the above object can be obtained, leading to the present invention.

<Structure of the Invention> According to the present invention, (a) filling the entire internal space of the mold or a specific area with solvent-soluble inorganic/organic compound particles; (b) press-fitting a wax agent into the mold and forming the model; (c) immersing the above model in a solvent and dissolving and removing the solvent-soluble inorganic/organic compound quantum to obtain a porous wax agent model; (d) using the above porous wax agent model to obtain a lost wax model. forming a mold by a method and injecting molten metal into the mold to obtain a porous metal casting; (e) cleaning mold sand grains that have entered the porous portion of the porous metal casting. A method for manufacturing a porous metal casting is provided.

The present invention will be explained in detail below based on FIGS. 1 to 4.

As shown in FIG. 1, a mold 1 used in the present invention is, for example, a split mold having an upper mold 1a and a lower mold 1b that cooperate to form an internal space 2. A wax agent pressure inlet 5 communicating with is formed. This wax agent injection port 5 is an opening for press-fitting the wax agent 4 into the internal space 2 as described later.

The material for forming the mold 1 is not particularly limited as long as it is a structural material with a predetermined strength, and may be any material such as a metal mold, a rubber mold, or an organic resin mold.
As long as it is a container with a bottom, it can be of any shape such as prismatic, cylindrical, truncated pyramid, truncated cone, cube, etc., but a wax agent pressure inlet as described above is formed at the top of the container to communicate with the internal space. Must have been.

The solvent-soluble inorganic/organic compound particles 3 to be filled in the entire area or specific area of the internal space 2 of the mold 1 are dissolved in an appropriate solvent such as water, an organic solvent such as acetone, or carbon tetrachloride, or an acid such as dilute hydrochloric acid. For example, carbohydrates such as sugar, polymeric compounds such as expanded polystyrene beads, or metal salts such as sodium chloride and sodium carbonate are preferably used.

Although the particle size of these inorganic/organic compounds 3 is not particularly limited, the particle size is preferably 200 to 500 μm in order to produce an implant material for implantation in a human body.

When the inorganic/organic compound particles 3 are filled in the entire area or a specific area of the internal space 2 of the mold 1, these particles 3 contact and connect with each other, and some of them are in contact with the inner wall surface of the mold 1. There is a need.

Otherwise, as will be described later, it will be difficult to dissolve and remove the inorganic/organic compound particles 3.

After filling the mold 1 with a predetermined amount of the inorganic/organic compound 3, the wax agent 4 is press-fitted into the remaining space from the wax agent injection port 5 to form a model consisting of the inorganic/organic compound 3 and the wax agent 4. get.

The wax agent 4 is not particularly limited as long as it does not dissolve the inorganic/organic compound particles 3, but wax, organic resin, etc. are suitable, for example.

This wax agent 4 must generally surround each of the particles 3 mentioned above. The term "approximately" used here is intended to facilitate the dissolution and removal of the particles 3, which will be described later, by surrounding the connecting portions of the particles 3 with the wax agent 4 more loosely than completely.

The model thus obtained is taken out from the mold 1 by removing the upper mold 1a and lower mold 1b of the mold 1, and is immersed in a solvent to dissolve and remove the solvent-soluble particles 3, as shown in FIG. A porous wax agent model 6 is obtained.

In addition, since the mold 1 can withstand continuous use rather than one-time use, it is possible to reduce manufacturing process costs.

Using the porous wax model 6 thus obtained or the model having a porous layer on a specific surface thereof, a mold is formed by the usual lost wax method. That is, as shown in FIG. 3, the porous voids of the porous wax model 6 are immersed in slurry 11 to form a shell-like outer shell. Note that the outside of the shell-like shell is generally made of sand. Slurry 1
1, for example, Cab%MgO%ZrO2, Y20
3rd grade is used.

Thereafter, the wax agent 4 is eluted by high-temperature, high-pressure steam treatment or other methods to obtain a mold (lost wax mold) 10 as shown in FIG.

After pouring molten metal into the mold 10 through the sprue 13 and solidifying it, the outer frame 12 is fixed by a mechanical or chemical method.
is removed to form a porous metal casting body 8 as shown in FIG.
get.

As the metal or alloy used in the manufacturing method of the present invention, almost all metals or alloys can be used, such as cast iron, lead, zinc, tin, aluminum, gold, which are used in ordinary porous metal bodies, Examples include silver, copper, alloys thereof, high melting point active metals such as titanium or zirconium, and alloys thereof.

The mold sand grains that have entered the porous portion 9 of the porous metal casting 8 obtained as described above are removed and cleaned by mechanical or chemical methods.

Methods for thoroughly removing these mold sand grains include, for example, high-pressure water washing or sandblasting, and methods for chemically removing them include, for example, pickling or alkali treatment.

That is, according to the present invention, since the porous layer is integrally molded by means of casting, the porous layer is difficult to be destroyed even by loads such as external pressure, and a stable high-quality porous metal cast body can be obtained. can be obtained.

<Example> The present invention will be explained in more detail below based on examples.

(Example 1) Styrofoam beads with a particle size of 0.3 to 0.8 mm were filled into a mold, and wax was then press-fitted into a mold of 10x40x2.
A plate-shaped wax model of mg+ was obtained. This model was immersed in acetone to elute the expanded polystyrene beads, and washed with water to form a porous wax model.

Following the procedure of the lost wax method, a sprue, a sprue, etc. were added and placed in a casting flask, and a MgO grade refractory lath slurry was placed there, dewaxed, and fired, followed by differential pressure casting of the titanium alloy.

After the alloy solidifies, the MgO refractory material is completely removed by sandblasting, ultrasonic cleaning, and pickling.
A porous metal casting made of titanium alloy was obtained, which had numerous connected pores with a diameter of 0.3 to 0.8 square meters inside.

When this porous cast body was used as an in-brand test piece for implantation in the bone of an animal, it was observed that bone tissue had grown within the pores of the test piece.

(Example 2) After filling a mold with fructose with a particle size of 0.2 to 0.5H, wax was press-fitted to produce a plate-shaped wax model of 50 x 50 x 2 mm, and the fructose was washed away with hot water to make it porous. It was made into a wax model. This was molded to a predetermined size and attached to the bone joint part of a wax model for an artificial knee joint. Following the lost wax method, sprues, sprues, etc. were added and coated with Y, O, and slurry. After that, it was coated with a backup coating, molded, dewaxed, and made into a ceramic shell mold.

A titanium alloy is poured into this mold using a centrifugal casting method, and after the alloy solidifies, it is sandblasted and acid treated.
, O, the refractory was completely removed.

In this way, it was possible to manufacture a titanium alloy artificial knee joint having a porous layer with a thickness of 2 mm, in which countless connected pores with a diameter of 200 to 500 μm exist on the bone joint surface, that is, a porous layer with a thickness of 2 fflI11. .

As mentioned above, materials that are implanted into bone, such as orthopedic artificial bones or dental artificial tooth roots, have a 20% concentration on the contact surface with the bone in order to effectively bond with the bone tissue.
It is necessary to provide unevenness of 0 to 300 μm.
-Layer Effectively, it is required to form a group of connected pores, that is, a porous layer.

Therefore, according to this example, a porous metal casting that satisfies this condition could be obtained.

<Effects of the Invention> As detailed above, according to the present invention, the porous metal body can be integrally molded by means of casting, so that porous metal castings that are difficult to break even under loads such as external pressure can be obtained. It is possible to provide a technology that can industrially manufacture bodies at low cost and with stable quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a state in which inorganic/organic compound particles and a wax agent are press-fitted into a mold. FIG. 2 is a schematic cross-sectional view of a porous wax agent model. FIG. 3 is a schematic cross-sectional view of a mold obtained by the lost wax method. FIG. 4 is a schematic cross-sectional view of a porous metal casting. Explanation of symbols 1... Mold, 2... Internal space, 3... Solvent soluble inorganic/organic compound particles, 4... Wax agent, 5... Wax agent injection port, 6... Porous Wax agent model, 8... Porous metal mold body, 9... Porous portion, 10... Mold (lost wax mold), 11... Slurry, 12... Outer frame, 13... sprue

Claims (1)

[Claims] (a) A step of filling the entire internal space of the mold or a specific region with solvent-soluble inorganic/organic compound particles, (b) A step of press-fitting a wax agent into the mold to obtain a model, (c) ) A step of immersing the above model in a solvent and dissolving and removing the solvent-soluble inorganic/organic compound particles to obtain a porous wax agent model; (d) Using the above porous wax agent model, molding a mold by a lost wax method. and a step of obtaining a porous metal casting after injecting molten metal into the mold; (e) a step of cleaning mold sand grains that have entered the porous portion of the porous metal casting. A method for manufacturing a porous metal casting body.